Purification of petroleum distillates containing naphthenic acids

ABSTRACT

A process for purifying a heavy petroleum distillate containing naphthenic acids by the novel intermixing of a caustic solution whereby no significant inverse emulsions are formed having a continuous aqueous phase and an internal hydrocarbon phase. The caustic solution is a fine droplet dispersion of an aqueous alkali metal hydroxide within an inert or non-reactive carrier hydrocarbon. An electrical field separates the intermixed distillate and caustic solution into a treated heavy petroleum distillate and an aqueous mixture of excess alkali metal hydroxide and salts of naphthenic acids.

United States Patent Jarrell PURIFICATION OF PETROLEUM DISTILLATES CONTAINING NAPHTHENIC ACIDS Primary Examiner-T. M. Tufariello [75] Inventor: William Grant Jarrell, Bellaire, Tex. Attorney Agent or FumflEm Bedm" [73] Assignee: Petrolite Corporation, St. Louis, [57] ABSTRACT A process for purifying a heavy petroleum distillate [22] Filed; June 22, 1973 containing naphthenic acids by the novel intermixing of a caustic solution whereby no significant inverse [21] PP BIO-1372726 emulsions are formed having a continuous aqueous phase and an internal hydrocarbon phase. The caustic 52 us. c1. 204/190 Solution is a fine droplet dispersion of an aqueous [51] Int. Cl. B03c 5/00 kali metal hydroxide Within ins-Fl 0r "(m-reactive [58] Field of Search 204/189, 190, 188 Carrier hydrocarbon An electrical field Separates the intermixed distillate and caustic solution into a treated 5 References Cited heavy petroleum distillate and an aqueous mixture of UNITED STATES PATENTS excess alkali metal hydroxide and salts of naphthenic 'ds. 2,447,530 8/1948 Perkins, Jr. ..204/l90 acl 2,395,011 2/1946 Perkins, Jr. .0 204/190 10 Claims, 1 Drawing Figure flaw/W517 35 HZAI/VflUT/ZA/iff 34d 25 27 i r /5 :4 36 32a zaj 0% 7 1 1 a .J/a l 350 272L833 lO/l955 Del'oe et al. 208/273 PURIFICATION OF PETROLEUM DISTILLATES CONTAINING NAPHTHENIC ACIDS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the separation of immiscible liquid mixtures; and more particularly, it relates to the resolution of dispersed water within hydrocarbons by a combination of electrical field treatment.

2. Description of the Prior Art In the refining of crude oils, various distillation and separating procedures are employed which produce a variety of distillates having great commercial value. One of these distillates resides in a boiling range above kerosenes, and encompasses the heating oils and other intermediate distillate portions with boiling ranges below the lubricating oil stocks. For practical purposes, these distillates are known as heavy petroleum distillates and usually reside within boiling ranges of between about 425 F. and about 675 F. However, some of the heavy petroleum distillates may have initial and end boiling points slightly below and slightly above this range. For various reasons, the preparation of commercial products require treating the heavy petroleum distillates with alkaline materials for removing undesired acidulous components. The heavy petroleum distillate is intimately contacted with an aqueous caustic solution of between 4 and 35 Be in strength. Usually the aqueous caustic solution is employed in a volumetric ratio between 5 and 25% of the heavy distillate stream being treated. The resultant intimate contacting between the aqueous caustic solution and the heavy petroleum distillate produces an emulsion having a continuous petroleum phase with the aqueous caustic phase carried as a fine dispersion. The resultant emulsion is subjected to a phase separation process, and preferably, to a process employing electrical fields for coalescence of the aqueous caustic phase from the purified heavy petroleum distillate phase. Usually, the electrical field readily coalesces the dispersed aqueous caustic solution from the continuous hydrocarbon phase to produce a product having very commercial acceptable characteristics.

In some cases, and especially in connection with the refining of naphthenic based crude oil, the direct intimate admixing of an aqueous caustic solution into a heavy petroleum distillate produces not only the dispersion of the aqueous caustic phase within the continuous heavy petroleum distillate phase, but concomitantly, there is formeda small portion of an inverse, mayonnaise-like, water-continuous emulsion. In the inverse emulsion, a small portion of the heavy petroleum distillate is dispersed within the aqueous phase formed of the aqueous metal hydroxide and naphthenic acid salts thereof. Not all naphthenic based crude oils produce this inverse, mayonnaise-likeemulsion. In addition, the chemistry responsible'for producing such inverse, mayonnaise-like emulsions during the processing of naphthenic based crude oil is'not completely under-- stood at this time. Attempts to reproduce the inverse mayonnaise-like emulsion have not always been successful within the laboratory. The inverse mayonnaiselike emulsion has been formed where a relatively large mass or body of the aqueous caustic solution is beingintermixed with a smaller volume of the heavy petroleum distillate and in the presence of some stabilizing agent. Although the relative amount of the inverse mayonnaise-like emulsion is small, substantial problems are created by them in subsequent refining operations.

Various processes have been proposed for avoiding these inverse emulsions. The particular parameters of process control for preventing formation of any inverse mayonnaise-like emulsion are so critical that they cannot be readily carried out in conventional refinery .operations. Specialized mixing apparatus for dispersing directly the aqueous caustic solution into the heavy petroleum distillate has borne promise. However, the relatively precise adjustment of the mixing apparatus requires careful attention by refinery personnel to produce the dispersion of the aqueous caustic phase into the heavy petroleum distillate without producingany significant amounts of the inverse mayonnaise-like emulsion. For example, an apparatus producing this mixing function is shown in U.S. Pat. No. 2,527,689. This patent also precisely describes the operation of the unique apparatus in preventing the generation of the oil-in-water, inverse type of emulsions.

Although the amounts of the inverse, mayonnaiselike emulsion produced during refinery operation is not great, even relatively small amounts produce difficultto-handle situations in what otherwise are highly reliable processing equipment. For example, electric field treaters, such as shown in U.S. Pat. No. 3,342,720,

have provided an excellent system for resolving the oilcontinuous emulsion containing a very fine dispersion of the aqueous caustic solution within the heavy petroleum distillate. Equipment described in this patent are capable of producing a heavy petroleum distillate without any residual acidity, a water content of less than 1 ppm, and a residual sodium ion content of less than.Q.5 ppm. The efficiency of the electric field resolutionof the oil-continuous emulsion within such industry accepted equipment is clearly indicated by the excellent results obtained in refinery systems. However, no electric field treater can tolerate the entry of the inverse mayonnaise-like emulsion into the electric field. The inverse emulsion will short-circuit the energized electrode assembly to adjacent electrically grounded portions of the treater. For example, the electric field in the treater causes the inverse mayonnaise-like emulsion to collect as a layer beneath the electric field and above the oil-water interface maintained in such treater. This interface layer of inverse emulsion continues to build in thickness until it reaches the energized electrode assembly within the treater. The inverse emulsion is water-continuous, and its contact withthe energized electrode assembly causes a short+circuiting condition in the treater. As a result, the treater suffers loss of its normally high efficiency in separatingoilcontinuous emulsions into a dispersed aqueous caustic solution phase and the purified heavy petroleum distillate phase.

Prior attempts to correct this problem have required expensive chemical pretreatment and precise quality control of the streams entering the electric field treater. The present invention is directed toward a process where the electric field treaters are arranged to operate without any significant accumulation or buildup of an interface layer of the inverse emulsion. The heavy petroleum distillate is contacted intimately with conventional amounts of aqueous caustic solution. However, this caustic solution is introduced into the stream being treated in a novel manner which prevents formation of any significant amounts of the inverse emulsion. Also, the resulting hydrocarbon-continuous emulsion containing dispersed caustic solution is resolved immediately in an electrical field before any significant amounts of inverse emulsion could be formed by internal or external surface tension effects.

SUMMARY OF THE INVENTION In accordance with this invention, there is provided a process for purifying a heavy petroleum distillate containing naphthenic acids. A small amount of a carrier hydrocarbon is provided for this process, which hydrocarbon is substantially free of soap-producing quantities of naphthenic acids. An aqueous alkali metal hydroxide is dispersed as a uniform dispersion of fine droplets within the carrier hydrocarbon. A first stream of the heavy petroleum distillate and a second stream of the carrier hydrocarbon with dispersed aqueous alkali metal hydroxide are introduced into a common conduit and then mixed to disperse the carrier hydrocarbon uniformly throughout the heavy petroleum distillate stream. Immediately thereafter, an electrical field separates these intermixed streams into a purified heavy hydrocarbon distillate phase, and an aqueous mixture of excess alkali metal hydroxide and the corresponding salts of naphthenic acid. This separation occurs before any inverse emulsion can form to affect the electrical field effects.

DESCRIPTION OF THE DRAWING The drawing is a schematic flow diagram of a two stage treating system for removing acidulous materials from a heavy petroleum distillate in accordance with the process of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS The process of the present invention may be practised upon heavy petroleum distillates derived from any type of crude oil or from any hydrocarbon source, and in any suitable electrical field treater capable of electrically resolving water-in-hydrocarbon emulsions. The process is especially suited for the processing of heavy petroleum distillates derived from viscous naphthenic based crude oils. However, the present process may be readily employed with a variety of crude oils which may form at least a small amount of the inverse mayonnaiselike water-continuous emulsions upon intimate contact with aqueous caustic solutions. In particular, the present process may be practised without requiring an intimate knowledge of the inverse emulsion forming characteristics of the crude oil from which the heavy petroleum distillate is derived.

The present process can be practised in any suitable electrical field treater which is capable of electrically resolving water-in-hydrocarbon emulsions or dispersions. For example, the apparatus illustrated in FIGS. 7, 8, and 9 of U.S. Pat. No. 3,342,720 has found an especial utility within the refinery industry for such purposes, and is well suited to carrying out the steps of the present process. However, the construction and opera tion of the electrical field treater is not critical to the present process. It needs only to provide a suitable electrical field and phase separation conditions in which a purified heavy petroleum distillate phase is separated from a coalesced aqueous mixture comprising aqueous alkali metal hydroxide and naphthenic acid salts. For example, the electrical field treater can employ energized electrodes which are spaced between three and eleven inches from one another. The electrical potential applied to these electrodes can vary in gradient of an effective D.C. electric field between about 1,000 and 10,000 volts per inch. The magnitude of the gradient, or the applied potential, within the electrical field of the treater is not critical to the practice of the present process.

Although a single electrical field treater may be employed to carry out the present process, it is preferred to employ two electric field treaters arranged for series flow of the heavy petroleum distillate thereby forming two stage treatment. Such as arrangement is available commercially as a two stage Electrofining operation. The term Electrofining is a trademark denoting a process which is commonly employed for the processing of distillates in a refinery by their treatment through the intimate dispersion of an aqueous chemical with subsequent electrical field resolution to provide a purified distillate phase.

Referring now to the drawing, there is shown a two stage distillate treating operation conducted with two electrical field treaters l1 and 12 interconnected for series flow of the heavy petroleum distillate. The distillate passes first through the treater l1 and then through the treater 12. The treaters 11 and 12 are shown substantially identical in structure. Therefore, the various elements of these treaters will be described specifically relative only to the treater 11, and it is to be understood that the treater 12 has like elements designated by like reference numerals but carrying the subscript (1" for purposes of the present description unless the like elements carry different reference numerals and are individually described.

The treater 11 is formed of a horizontally disposed, cylindrical metal vessel 13 which carries an inlet 14, a purified heavy distillate outlet 16, and an aqueous mixture outlet 17. The inlet 14 connects to a perforated pipe distributor 18 which extends substantially through the length of the vessel 13. The inlet 14 receives an oilcontinuous emulsion formed by the intimate dispersion of an aqueous caustic solution of this invention into the distillate phase. Preferably, the distillate phase is at above F. The distillate phase is introduced from an inlet conduit 39 through a block valve 40 and a pressure-controlled mixing valve 41 into the inlet 14. The electrical field in the treater 11 resolves the emulsion into a purified heavy distillate and an aqueous mixture phase. The electrical field section within the treater 11 can be of the construction described in U.S. Pat. No. 3,342,720, and in particular, as shown in FIGS. 7, 8, and 9. This treater construction includes a grounded electrode assembly 19 which may take the form of metal plates forming vertical cells 22 with intersecting vertical walls 21. The cells 22 have open bottoms 24 with their upper extremities enclosed by a top cover 26.

The top cover 26 carries an orifice 27 in each of the cells 22. The vertical cells 22 may have any configuration, but are preferably rectangular in cross-section with their longitudinal dimension extending vertically at least eight times their horizontal dimension. All fluid flow withinthe cells 22 passes through the orifices 27 and each orificeis arranged to create apressure drop of a few ounces of water as a restriction to the flow of fluids through top cover 26. However, this small backpressure created across each orifice 27 is sufficent that will beat a uniform rate. Thus, the fluids flow upwardly through all of the cells 22 at substantially the same vertical rise within the electric treater 11. The grounded electrode assembly 19 is secured to the vessel 13 in any suitable fashion such as by bolting or welding.

Each of the cells 22 carries an axially disposed energized electrode 28 supported upon a rack 29. The elec trode 28 is held in electrical isolation in each cell 22 by insulators 31 carried upon supporting rods 32 and 33. The electrodes 28 can be energized from any suitable power supply means, but they preferably receive a high potential DC. current from an external power source.

For example, a DC. power pack 34 is mountedatop the vessel 13 and receives power from polyphase AC. power sources'within the refinery. The power pack 34 includes transformers and rectifier means to produce relatively high potential D.C. currents which are applied to the electrodes 28 through an insulating conduit 35, entrance bushing 36, and a flexible lead 37 connected to the rack 29.

During operation of the treater 11, an aqueous mixture body having a fixed interface is maintained within the lower portion of the electric treater 11. For this purpose, the outlet 17 includes a motor valve 42 actuated by a float controller 43. The outlet 17 is connected to a system for removing the aqueous mixture which accumulates in the lower portion of the treater 11. The aqueous mixture is withdrawn at a rate which prevents any substantial vertical change in the interface 15. This aqueous mixture is the blend of the alkali metal hydroxide salts of naphthenic acids and any exinert or non-reactive hydrocarbon carrier. The carrier hydrocarbon should have physical and chemical properties such that it can be introduced in small quantities into the heavy distillate upstream of the inlet 14 without any significant effect upon the purified heavy distillate provided by either the treater 11 or the treater 12. ln particular, the hydrocarbon carrier should have only a very small amount of naphthenic acids, and the actual amount of the organic acidic material should be insufficient to form the oil-insoluble soaps of the reaction products of these acids and the alkali metal hydroxide. In no event should the carrier hydrocarbon contain such amounts of the organic acidic'material that an inverse emulsion will form upon contact with a greater volume of an aqueous alkali metal hydroxide solution.

stream may be taken from outlets 16 or 16a. A carrier hydrocarbon derived from this source gives unusually good results since the physical and chemical properties are very close to the heavy petroleum distillate to be purified. For example, the more closely alike the density, viscosity, surface tension and percentile molecular weight distributions are between the carrier hydrocarbon and the heavy petroleum distillate, the less the chance that any inverse emulsion can be formed. Also, the dispersed fine droplets of the aqueous metal hydroxide within the carrier hydrocarbon are less effected in particle size distributions upon being intermixed into the heavy petroleum distillate entering the inlet 14. As a result, the conditions for producing any inverse emulsions are, for practical purposes, substantially avoided.

Once a source of the carrier hydrocarbon is obtained, the aqueous alkali metal hydroxide can be dispersed therein as a uniform dispersion of fine droplets. Highly acceptable results are obtained when these fine droplets reside with diameter sizes in the range of from 1 to 10 microns. Best results can be expected when the majority of the fine droplets have diameters more close to 1 micron than to the 10 micron size. Larger droplet sizes may be usedif the variant purification results remain acceptable.

Any system may be used to disperse fine droplets of the aqueous metal hydroxide into the carrier hydrocarbon. For example, a mechanical or sonic mixer may be used for this purpose. However, good results have been obtained using an air-jet mixer which is illustrated in the drawing. The carrier hydrocarbon, which may be taken from outlet 16a, is introduced at regulated rates through inlet 59 and metering valve 61 into mixingvessel 56. A regulated flow of the aqueous alkali metal hydroxide (e.g., caustic soda) is added to the vessel 56 through inlet 57 and metering valve 58. The aqueous metal hydroxide is dispersed into the carrier hydrocarbon by a jet mixer 64 driven by air introduced through inlet 62 and regulated in amount by the valve 63. The jet mixer is constructed to produce the desired droplet sizes of the aqueous alkali metal hydroxide uniformly throughout the carrier hydrocarbon in the vessel 56. The amount of air provided the jet mixer 64 insures this result. Also itis expected that the presence of air in the vessel produces an oxidizing and cleaning effect upon the fluids in the vessel 56. As aresult of the cleaning effect, the ultimate purification of the heavy petroleum distillate is enhanced.

The finely dispersed aqueous alkali metal hydroxide and carrier hydrocarbon are usually used in volumetric ratios of between 1 to 20, and l to l in the ultimate mixture. Good results have been obtained wherethe dispersed aqueous alkali metalhydroxide is present in an amount less than 40 per cent (by volume) of the total hydrocarbon-continuous emulsion produced 1 in vessel 5.6. Best results appear to be consistantly obtained whenthe aqueous metal hydroxide is present in 25% by volume ofthe combined streams produced within the vessel 56.

The amount and strength ofthe aqueous alkali metal hydroxide solution dispersedinto the carrier hydrocarbon is adjusted by conventional treating practices to obtain the removal of the acidu-lous material carried in thejheavy petroleumdistillate. The-alkali metal hydroxideis usually employed in about -115 per cent of the stoich'iometric amount relative to the naphthenic acids desired to be removed from the heavy petroleum distillate stream at inlet 14. Good results are obtained with 5 'B'aume caustic solutions. The alkali metal hydroxide (e.g., sodium or potassium hydroxide) is usually employed in strengths between- 0.5 and 10% by weight. in water, and in volumesof between 0.1 and 5% relative to the heavypetroleum-distillate stream'at the mixing valve 41. The dispersed aqueous alkali metal hydroxide within the carrier hydrocarbon is removed by outlet 65 from the vessel 56, and passes through a pump 66 for metered entry into conduit 67. Then, this stream joins the heavy petroleum entering the mixing valve 41. The valve 41 is adjusted so that the dispersed aqueous alkali metal hydroxide maintains relatively constant in droplet sizes while being uniformly distributed within the heavy petroleum distillate entering the treater 11. The finely dispersed aqueous alkali metal hydroxide reacts within the continuous hydrocarbon phase and forms a finely dispersed aqueous mixture which includes excess metal hydroxide and the corresponding salts of naphthenic acids.

The mixing valve 41 provides an intimate intermixing of the dispersed aqueous solution within the heavy distillate upstream at the inlet 14. This distillatecontinuous emulsion passes immediately from the mixing valve 41 to the inlet 14, through the distributor 18 and then rises in the vessel 13 upwardly into the electrical field provided by the energized electrode 28 in the vertical cells 22. The emulsion should enter the electrical field before any significant phase separation occurs. As a result, no inverse emulsion can be formed by internal or external surface tension effects. The emulsion usually should enter the electrical field within. a few minutes of formation. Good results are to be expected where initial electrical field separation of the emulsion occurs within a minute or less of its formation. The aqueous mixture phase coalesces from the heavy petroleum distillate and gravitates downwardly to the lower extremity of the treater 11 below the interface 15. The purified heavy distillate passes through the orifices 27 and then moves upwardly into the outlet 16 for delivery to a subsequent utilization.

The aqueous mixture phase in the treater 11 is passed through the valve 42 into an outlet line 45 for transmittal to a subsequent utilization. This material is substantially free of heavy petroleum distillate and comprises a mixture of the alkali metal hydroxide salts of naphthenic acids, unreacted or residual aqueous alkali metal hydroxide, and other aqueous phase materials derived in the treater 11. This aqueous mixture has a relatively high commercial value and is generally commercialized under the name naphthenic acid soaps. The aqueous mixture is passed from the conduit 45 into a soap re ceiving tank 71 where it is held in storage until subsequent utilization. For this purpose, the aqueous mixture is removed through an outlet 72 by a pump 73 and passed through a control valve 74 to the desired subsequent utilization.

Preferably, the purified heavy distillate is moved through an outlet conduit 46 to the electric treater 12 in a subsequent water washing operation. For this purpose, the purified heavy distillate is intermixed with fresh water (-15% by volume) introduced into the conduit 46 through an inlet 47. Then, the fresh water and distillate are passed through a pressure controlled mixing valve 48 which produces an intimate dispersion of the fresh water within the heavy distillate prior to its entry into the inlet of 14a of the treater 12. By fresh water, for purposes of the present process, is meant a water which may be potable or any water having a sufficiently low content of inorganic materials that it can remove desirably the residual water soluble materials from the purifiedheavydistillate. The operation of the treater 12 is substantially identical to the treater 11. A

water-washed, purified heavy distillate stream is removed through the outlet 16a from the treater 12 and sent to a subsequent utilization. The controller 43a operates a motor valve 42a in the outlet 17a to remove the effluent water from the treater 12 to a subsequent disposal.

The dispersion of the aqueous alkali metal hydroxide solution within the carrier hydrocarbon has many advantages in addition to precise control of droplet sizes. The volumetric control of amounts of the caustic solution is greatly simplified since the flow through the pump 66 is easily adjusted. Also, the composition of the prepared emulsion from the vessel 56 can be selectively varied between several relatively stable compositioned emulsions. Thus, no precise control of the caustic solution in volume or amount of alkali metal hydroxide is encountered in the present process. Likewise, the rate of flow of the heavy petroleum distillate does not upset the caustic solution composition or droplet sizes. The hydrocarbon-continous emulsion entering the electrical field in treater 11 is resolved before any inverse emulsion is encountered. Thus, no inverse emulsion to create prior art problems can be produced from the initial contact of the heavy petroleum distillate with the aqueous alkali metal hydroxide solution until the electrical field has produced the purified heavy petroleum distillate by immediate emulsion resolution.

From the foregoing, it will be apparent that there has been described a novel process for purifying a heavy petroleum distillate containing naphthenic acids without the problems heretofore encountered during refinery process operation. Various modifications and alterations in the desired process will be apparent to those skilled in the art which do not depart from the spirit of the present invention. For this reason, these changes are desired to be included within the scope of the appended claims. The appended claims define the present invention; the foregoing description is to be employed for setting forth the present invention embodiments as illustrative in nature. What is claimed is: l. A process for purifying a heavy petroleum distillate containing naphthenic acids comprising:

a. providing a carrier hydrocarbon substantially free of soap-producing quantities of naphthenic acids and compatible with the heavy petroleum distillate;

b. dispersing an aqueous alkali metal hydroxide into the carrier hydrocarbon wherein said aqueous alkali metal hydroxide resides within the carrier hydrocarbon as a uniform dispersion of fine droplets in a hydrocarbon-continuous emulsion;

c. introducing a first stream of the heavy petroleum distillate and a second stream of the carrier hydrocarbon from step (b) into a common conduit;

d. passing the first and second-streams from the common conduit through a mixing means for dispersing the carrier hydrocarbon uniformly throughout the first stream of heavy petroleum distillate containing naphthenic acids; and

e. subjecting the first and second streams, immediately after mixing, and before any significant phase separation occurs,-to-an electrical field to separate a purified heavy. hydrocarbon distillate phase from an aqueous mixture. of excess alkali metal hydroxide and the alkali metal hydroxide salts of naphthenic acids, and said purified heavy hydrocarbon distillate stream containing the carrier hydrocarbon.

2. The process of claim 1 wherein the alkali metal hydroxide is dispersed into the carrier hydrocarbon in amounts not in excess of 50 percent by weight of the emulsion produced in step (b).

3. The process of claim 1 wherein the alkali metal hydroxide is dispersed into the carrier hydrocarbon in amounts between and 40 per cent by weight of the emulsion produced in step (b).

4. The process of claim 2 wherein the alkali metal hydroxide dispersed into the carrier hydrocarbon to produce the emulsion is an aqueous solution of caustic soda between 0.5 and 10 per cent by weight and water.

5. The process of claim 2 wherein the alkali metal hydroxide dispersed into the carrier hydrocarbon to produce the emulsion is an aqueous solution of caustic soda having a concentration of about 5 Baume.

6. The process of claim 1 wherein said aqueous alkali metal hydroxide dispersed in said carrier hydrocarbon in step (b) has a majority of droplet sizes in the range between 1 and 10 microns.

7. The process of claim 1 whereinsaid purified heavy hydrocarbon distillate stream containing the carrier hydrocarbon from step (e) is intimately contacted with wash water and separated into a highly purified heavy petroleum distillate phase substantially free of metal alkali hydroxide salts of naphthenic acids and wash water carrying extracted alkali metal hydroxide salts of naphthenic acids.

8. The process of claim 7 wherein the separation of the combined portions of heavy petroleum distillate and wash water is effected under the influence of an electrical field.

9. The process of claim 1 wherein the aqueous alkali metal hydroxide is dispersed into the carrier hydrocarbon using a stream of air applied through a mixing jet.

10. The process of claim 1 wherein the carrier hydrocarbon is provided by a small portion of the purified heavy petroleum distillate phase separated in an elec- 

1. A PROCESS FOR PURIFYING A HEAVY PETROLEUM DISTILLATE CONTAINING NAPHTHENIC ACIDS COMPRISING: A. PROVIDING A CARRIER HYDROCARBON SUBSTANTIALLY FREE OF SOAP-PRODUCING QUANTITIES OF NAPHTHENIC ACIDS AND COMPATIBLE WITH THE HEAVY PETROLEUM DISTILLATE; B. DISPERSING AN AQUEOUS ALKALI METAL HYDROXIDE INTO THE CARRIER HYDROCARBON WHEREIN SAID AQUEOUS ALKALI METAL HYDROXIDE RESIDES WITHIN THE CARRIER HYDROCARBON AS A UNIFORM DISPERSION OF FINE DROPLETS IN A HYDROCARBONCONTINUOUS EMULSION; C. INTRODUCING A FISRT STREAM OF THE HEAVY PETROLEUM DISTILLATE AND A SECOND STREAM OF THE CARRIER HYDROCARBON FROM STEP (B) INTO A COMMON CONDUIT; D. PASSING THE FIRST AND SECOND STREAMS FROM THE COMMON CONDUIT THROUGH A MIXING MEANS FOR DISPERSING THE CARRIER HYDROCARBON UNIFORMLY THROUGHOUT THE FIRST STREAM OF HEAVY PETROLEUM DISTILLATE CONTAINING NAPHTHENIC ACIDS; AND E. SUBJECTING THE FIRST AND SECOND STREAMS, IMMEDIATELY AFTER MIXING, AND BEFORE ANY SIGNIFICANT PHASE SEPARATION OCCURS, TO AN ELECTRICAL FIELD TO SEPARATE A PURIFIED HEAVY HYDROCARBON DISTILLATE PHASE FROM AN AQUEOUS MIXTURE OF EXCESS ALKALI METAL HYDROXIDE AND THE ALKALI METAL HYDROXIDE SALTS OF NAPHTHENIC ACIDS, AND SAID PURIFIED HEAVY HYDROCARBON DISTILLATE STREAM CONTAINING THE CARRIER HYDROCARBON.
 2. The process of claim 1 wherein the alkali metal hydroxide is dispersed into the carrier hydrocarbon in amounts not in excess of 50 percent by weight of the emulsion produced in step (b).
 3. The process of claim 1 wherein the alkali metal hydroxide is dispersed into the carrier hydrocarbon in amounts between 10 and 40 per cent by weight of the emulsion produced in step (b).
 4. The process of claim 2 wherein the alkali metal hydroxide dispersed into the carrier hydrocarbon to produce the emulsion is an aqueous solution of caustic soda between 0.5 and 10 per cent by weight and water.
 5. The process of claim 2 wherein the alkali metal hydroxide dispersed into the carrier hydrocarbon to produce the emulsion is an aqueous solution of caustic soda having a concentration of about 5* Baume.
 6. The process of claim 1 wherein said aqueous alkali metal hydroxide dispersed in said carrier hydrocarbon in step (b) has a majority of droplet sizes in the range between 1 and 10 microns.
 7. The process of claim 1 whereinsaid purified heavy hydrocarbon distillate stream containing the carrier hydrocarbon from step (e) is intimately contacted with wash water and separated into a highly purified heavy petroleum distillate phase substantially free of metal alkali hydroxide salts of naphthenic acids and wash water carrying extracted alkali metal hydroxide salts of naphthenic acids.
 8. The process of claim 7 wherein the separation of the combined portions of heavy petroleum distillate and wash water is effected under the influence of an electrical field.
 9. The process of claim 1 wherein the aqueous alkali metal hydroxide is dispersed into the carrier hydrocarbon using a stream of air applied through a mixing jet.
 10. The process of claim 1 wherein the carrier hydrocarbon is provided by a small portion of the purified heavy petroleum distillate phase separated in an electrical field. 